Pretty hard. Passing it depends heavily on how good your team is as well as your items. My first time I attempted hard mode, I had both the "+ATK only in Hard Mode" AND the "+Def only in hard mode" items, yet I failed hard, losing Wrizz and still burning ~10 tears just to finish. Yet, I am also >>234824
, where I breezed right through hard mode when Shem had enough +damage items.
Since lab tokens are too important to me right now in order for me to get both Albedo and Ainz f2p, I don't tend to take the chance unless I'm supremely confident I can beat it.
The cunt who wrote this guidehttps://afkarenaguides.com/arcane-labyrinth/
claims he can consistently beat it without using a single thing of tears. I don't know if that's because he's at a certain level with furniture/SI that makes it easier or what, but I am certainly not at that point.